Control channel detection

ABSTRACT

A wireless device at least demodulates, descrambles and decodes a first control signal to generate a first signal. The wireless device processes the first signal by at least encoding, scrambling, modulating and scaling the first signal. The wireless device subtracts the processed first signal from received signals to generate a second signal. The wireless device at least demodulates, descrambles and decodes the second signal to generate a second control message.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 13/684,419,filed Nov. 23, 2012, which claims the benefit of U.S. ProvisionalApplication No. 61/567,094, filed Dec. 5, 2011, which is herebyincorporated by reference in its entirety.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Examples of several of the various embodiments of the present inventionare described herein with reference to the drawings, in which:

FIG. 1 is a diagram depicting example sets of OFDM subcarriers as per anaspect of an embodiment of the present invention;

FIG. 2 is a diagram depicting an example transmission time and receptiontime for two carriers as per an aspect of an embodiment of the presentinvention;

FIG. 3 is a diagram depicting OFDM radio resources as per an aspect ofan embodiment of the present invention;

FIG. 4 is a block diagram of a base station and a wireless device as peran aspect of an embodiment of the present invention;

FIG. 5 is a block diagram depicting a system for transmitting datatraffic over an OFDM radio system as per an aspect of an embodiment ofthe present invention;

FIG. 6 is a diagram depicting an example heterogeneous network as per anaspect of an embodiment of the present invention;

FIG. 7 is a diagram illustrating a few example interference scenarios asper an aspect of an embodiment of the present invention;

FIG. 8 is a diagram depicting an example almost blank subframe as per anaspect of an embodiment of the present invention;

FIG. 9 is an example almost blank subframe configuration as per anaspect of an embodiment of the present invention;

FIG. 10 is a diagram depicting an example wireless device configurationas per an aspect of an embodiment of the present invention;

FIG. 11 is a flow chart illustrating an example processing of controlformat indicator signal as per an aspect of an embodiment of the presentinvention;

FIG. 12 is a flow chart illustrating an example processing of physicalbroadcast signal as per an aspect of an embodiment of the presentinvention;

FIG. 13 is a flow chart illustrating an example processing ofsynchronization signal as per an aspect of an embodiment of the presentinvention;

FIG. 14 is a flow chart illustrating an example processing of referencesignals as per an aspect of an embodiment of the present invention; and

FIG. 15 is a flow chart illustrating transmission of control messages asper an aspect of an embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

Example embodiments of the present invention enable detection of controlchannels. Embodiments of the technology disclosed herein may be employedin the technical field of wireless communication systems. Moreparticularly, the embodiments of the technology disclosed herein mayrelate to detection of control channels in wireless communicationsystems.

Example embodiments of the invention may be implemented using variousphysical layer modulation and transmission mechanisms. Exampletransmission mechanisms may include, but are not limited to: CDMA (codedivision multiple access), OFDM (orthogonal frequency divisionmultiplexing), TDMA (time division multiple access), Wavelettechnologies, and/or the like. Hybrid transmission mechanisms such asTDMA/CDMA, and OFDM/CDMA may also be employed. Various modulationschemes may be applied for signal transmission in the physical layer.Examples of modulation schemes include, but are not limited to: phase,amplitude, code, a combination of these, and/or the like. An exampleradio transmission method may implement QAM (quadrature amplitudemodulation) using BPSK (binary phase shift keying), QPSK (quadraturephase shift keying), 16-QAM, 64-QAM, 256-QAM, and/or the like. Physicalradio transmission may be enhanced by dynamically or semi-dynamicallychanging the modulation and coding scheme depending on transmissionrequirements and radio conditions.

FIG. 1 is a diagram depicting example sets of OFDM subcarriers as per anaspect of an embodiment of the present invention. As illustrated in thisexample, arrow(s) in the diagram may depict a subcarrier in amulticarrier OFDM system. The OFDM system may use technology such asOFDM technology, SC-OFDM (single carrier-OFDM) technology, or the like.For example, arrow 101 shows a subcarrier transmitting informationsymbols. FIG. 1 is for illustration purposes, and a typical multicarrierOFDM system may include more subcarriers in a carrier. For example, thenumber of subcarriers in a carrier may be in the range of 10 to 10,000subcarriers. FIG. 1 shows two guard bands 106 and 107 in a transmissionband. As illustrated in FIG. 1, guard band 106 is between subcarriers103 and subcarriers 104. The example set of subcarriers A 102 includessubcarriers 103 and subcarriers 104. FIG. 1 also illustrates an exampleset of subcarriers B 105. As illustrated, there is no guard band betweenany two subcarriers in the example set of subcarriers B 105. Carriers ina multicarrier OFDM communication system may be contiguous carriers,non-contiguous carriers, or a combination of both contiguous andnon-contiguous carriers.

FIG. 2 is a diagram depicting an example transmission time and receptiontime for two carriers as per an aspect of an embodiment of the presentinvention. A multicarrier OFDM communication system may include one ormore carriers, for example, ranging from 1 to 10 carriers. Carrier A 204and carrier B 205 may have the same or different timing structures.Although FIG. 2 shows two synchronized carriers, carrier A 204 andcarrier B 205 may or may not be synchronized with each other. Differentradio frame structures may be supported for FDD (frequency divisionduplex) and TDD (time division duplex) duplex mechanisms. FIG. 2 showsan example FDD frame timing. Downlink and uplink transmissions may beorganized into radio frames 201. In this example, radio frame durationis 10 msec. Other frame durations, for example, in the range of 1 to 100msec may also be supported. In this example, each 10 ms radio frame 201may be divided into ten equally sized sub-frames 202. Other subframedurations such as including 0.5 msec, 1 msec, 2 msec, and 5 msec mayalso be supported. Sub-frame(s) may consist of two or more slots 206.For the example of FDD, 10 subframes may be available for downlinktransmission and 10 subframes may be available for uplink transmissionsin each 10 ms interval. Uplink and downlink transmissions may beseparated in the frequency domain. Slot(s) may include a plurality ofOFDM symbols 203. The number of OFDM symbols 203 in a slot 206 maydepend on the cyclic prefix length and subcarrier spacing.

In an example case of TDD, uplink and downlink transmissions may beseparated in the time domain. According to some of the various aspectsof embodiments, each 10 ms radio frame may include two half-frames of 5ms each. Half-frame(s) may include eight slots of length 0.5 ms andthree special fields: DwPTS (Downlink Pilot Time Slot), GP (GuardPeriod) and UpPTS (Uplink Pilot Time Slot). The length of DwPTS andUpPTS may be configurable subject to the total length of DwPTS, GP andUpPTS being equal to 1 ms. Both 5 ms and 10 ms switch-point periodicitymay be supported. In an example, subframe 1 in all configurations andsubframe 6 in configurations with 5 ms switch-point periodicity mayinclude DwPTS, GP and UpPTS. Subframe 6 in configurations with 10 msswitch-point periodicity may include DwPTS. Other subframes may includetwo equally sized slots. For this TDD example, GP may be employed fordownlink to uplink transition. Other subframes/fields may be assignedfor either downlink or uplink transmission. Other frame structures inaddition to the above two frame structures may also be supported, forexample in one example embodiment the frame duration may be selecteddynamically based on the packet sizes.

FIG. 3 is a diagram depicting OFDM radio resources as per an aspect ofan embodiment of the present invention. The resource grid structure intime 304 and frequency 305 is illustrated in FIG. 3. The quantity ofdownlink subcarriers or resource blocks (RB) (in this example 6 to 100RBs) may depend, at least in part, on the downlink transmissionbandwidth 306 configured in the cell. The smallest radio resource unitmay be called a resource element (e.g. 301). Resource elements may begrouped into resource blocks (e.g. 302). Resource blocks may be groupedinto larger radio resources called Resource Block Groups (RBG) (e.g.303). The transmitted signal in slot 206 may be described by one orseveral resource grids of a plurality of subcarriers and a plurality ofOFDM symbols. Resource blocks may be used to describe the mapping ofcertain physical channels to resource elements. Other pre-definedgroupings of physical resource elements may be implemented in the systemdepending on the radio technology. For example, 24 subcarriers may begrouped as a radio block for a duration of 5 msec.

Physical and virtual resource blocks may be defined. A physical resourceblock may be defined as N consecutive OFDM symbols in the time domainand M consecutive subcarriers in the frequency domain, wherein M and Nare integers. A physical resource block may include M×N resourceelements. In an illustrative example, a resource block may correspond toone slot in the time domain and 180 kHz in the frequency domain (for 15KHz subcarrier bandwidth and 12 subcarriers). A virtual resource blockmay be of the same size as a physical resource block. Various types ofvirtual resource blocks may be defined (e.g. virtual resource blocks oflocalized type and virtual resource blocks of distributed type). Forvarious types of virtual resource blocks, a pair of virtual resourceblocks over two slots in a subframe may be assigned together by a singlevirtual resource block number. Virtual resource blocks of localized typemay be mapped directly to physical resource blocks such that sequentialvirtual resource block k corresponds to physical resource block k.Alternatively, virtual resource blocks of distributed type may be mappedto physical resource blocks according to a predefined table or apredefined formula. Various configurations for radio resources may besupported under an OFDM framework, for example, a resource block may bedefined as including the subcarriers in the entire band for an allocatedtime duration.

According to some of the various aspects of embodiments, an antenna portmay be defined such that the channel over which a symbol on the antennaport is conveyed may be inferred from the channel over which anothersymbol on the same antenna port is conveyed. In some embodiments, theremay be one resource grid per antenna port. The set of antenna port(s)supported may depend on the reference signal configuration in the cell.Cell-specific reference signals may support a configuration of one, two,or four antenna port(s) and may be transmitted on antenna port(s) {0},{0, 1}, and {0, 1, 2, 3}, respectively. Multicast-broadcast referencesignals may be transmitted on antenna port 4. Wireless device-specificreference signals may be transmitted on antenna port(s) 5, 7, 8, or oneor several of ports {7, 8, 9, 10, 11, 12, 13, 14}. Positioning referencesignals may be transmitted on antenna port 6. Channel state information(CSI) reference signals may support a configuration of one, two, four oreight antenna port(s) and may be transmitted on antenna port(s) 15, {15,16}, {15, . . . , 18} and {15, . . . , 22}, respectively. Variousconfigurations for antenna configuration may be supported depending onthe number of antennas and the capability of the wireless devices andwireless base stations.

According to some embodiments, a radio resource framework using OFDMtechnology may be employed. Alternative embodiments may be implementedemploying other radio technologies. Example transmission mechanismsinclude, but are not limited to: CDMA, OFDM, TDMA, Wavelet technologies,and/or the like. Hybrid transmission mechanisms such as TDMA/CDMA, andOFDM/CDMA may also be employed.

FIG. 4 is an example block diagram of a base station 401 and a wirelessdevice 406, as per an aspect of an embodiment of the present invention.A communication network 400 may include at least one base station 401and at least one wireless device 406. The base station 401 may includeat least one communication interface 402, at least one processor 403,and at least one set of program code instructions 405 stored innon-transitory memory 404 and executable by the at least one processor403. The wireless device 406 may include at least one communicationinterface 407, at least one processor 408, and at least one set ofprogram code instructions 410 stored in non-transitory memory 409 andexecutable by the at least one processor 408. Communication interface402 in base station 401 may be configured to engage in communicationwith communication interface 407 in wireless device 406 via acommunication path that includes at least one wireless link 411.Wireless link 411 may be a bi-directional link. Communication interface407 in wireless device 406 may also be configured to engage in acommunication with communication interface 402 in base station 401. Basestation 401 and wireless device 406 may be configured to send andreceive data over wireless link 411 using multiple frequency carriers.According to some of the various aspects of embodiments, transceiver(s)may be employed. A transceiver is a device that includes both atransmitter and receiver. Transceivers may be employed in devices suchas wireless devices, base stations, relay nodes, and/or the like.Example embodiments for radio technology implemented in communicationinterface 402, 407 and wireless link 411 are illustrated are FIG. 1,FIG. 2, and FIG. 3. and associated text.

FIG. 5 is a block diagram depicting a system 500 for transmitting datatraffic generated by a wireless device 502 to a server 508 over amulticarrier OFDM radio according to one aspect of the illustrativeembodiments. The system 500 may include a Wireless CellularNetwork/Internet Network 507, which may function to provide connectivitybetween one or more wireless devices 502 (e.g., a cell phone, PDA(personal digital assistant), other wirelessly-equipped device, and/orthe like), one or more servers 508 (e.g. multimedia server, applicationservers, email servers, or database servers) and/or the like.

It should be understood, however, that this and other arrangementsdescribed herein are set forth for purposes of example only. As such,those skilled in the art will appreciate that other arrangements andother elements (e.g., machines, interfaces, functions, orders offunctions, etc.) may be used instead, some elements may be added, andsome elements may be omitted altogether. Further, as in mosttelecommunications applications, those skilled in the art willappreciate that many of the elements described herein are functionalentities that may be implemented as discrete or distributed componentsor in conjunction with other components, and in any suitable combinationand location. Still further, various functions described herein as beingperformed by one or more entities may be carried out by hardware,firmware and/or software logic in combination with hardware. Forinstance, various functions may be carried out by a processor executinga set of machine language instructions stored in memory.

As shown, the access network may include a plurality of base stations503 . . . 504. Base station 503 . . . 504 of the access network mayfunction to transmit and receive RF (radio frequency) radiation 505 . .. 506 at one or more carrier frequencies, and the RF radiation mayprovide one or more air interfaces over which the wireless device 502may communicate with the base stations 503 . . . 504. The user 501 mayuse the wireless device (or UE: user equipment) to receive data traffic,such as one or more multimedia files, data files, pictures, video files,or voice mails, etc. The wireless device 502 may include applicationssuch as web email, email applications, upload and ftp applications, MMS(multimedia messaging system) applications, or file sharingapplications. In another example embodiment, the wireless device 502 mayautomatically send traffic to a server 508 without direct involvement ofa user. For example, consider a wireless camera with automatic uploadfeature, or a video camera uploading videos to the remote server 508, ora personal computer equipped with an application transmitting traffic toa remote server.

One or more base stations 503 . . . 504 may define a correspondingwireless coverage area. The RF radiation 505 . . . 506 of the basestations 503 . . . 504 may carry communications between the WirelessCellular Network/Internet Network 507 and access device 502 according toany of a variety of protocols. For example, RF radiation 505 . . . 506may carry communications according to WiMAX (Worldwide Interoperabilityfor Microwave Access e.g., IEEE 802.16), LTE (long term evolution),microwave, satellite, MMDS (Multichannel Multipoint DistributionService), Wi-Fi (e.g., IEEE 802.11), Bluetooth, infrared, and otherprotocols now known or later developed. The communication between thewireless device 502 and the server 508 may be enabled by any networkingand transport technology for example TCP/IP (transport controlprotocol/Internet protocol), RTP (real time protocol), RTCP (real timecontrol protocol), HTTP (Hypertext Transfer Protocol) or any othernetworking protocol.

According to some of the various aspects of embodiments, an LTE networkmay include many base stations, providing a user plane (PDCP: packetdata convergence protocol/RLC: radio link control/MAC: media accesscontrol/PHY: physical) and control plane (RRC: radio resource control)protocol terminations towards the wireless device. The base station(s)may be interconnected with other base station(s) by means of an X2interface. The base stations may also be connected by means of an S1interface to an EPC (Evolved Packet Core). For example, the basestations may be interconnected to the MME (Mobility Management Entity)by means of the S1-MME interface and to the Serving Gateway (S-GW) bymeans of the S1-U interface. The S1 interface may support a many-to-manyrelation between MMEs/Serving Gateways and base stations. A base stationmay include many sectors for example: 1, 2, 3, 4, or 6 sectors. A basestation may include many cells, for example, ranging from 1 to 50 cellsor more. A cell may be categorized, for example, as a primary cell orsecondary cell. When carrier aggregation is configured, a wirelessdevice may have one RRC connection with the network. At RRC connectionestablishment/re-establishment/handover, one serving cell may providethe NAS (non-access stratum) mobility information (e.g. TAI-trackingarea identifier), and at RRC connection re-establishment/handover, oneserving cell may provide the security input. This cell may be referredto as the Primary Cell (PCell). In the downlink, the carriercorresponding to the PCell may be the Downlink Primary Component Carrier(DL PCC), while in the uplink, it may be the Uplink Primary ComponentCarrier (UL PCC). Depending on wireless device capabilities, SecondaryCells (SCells) may be configured to form together with the PCell a setof serving cells. In the downlink, the carrier corresponding to an SCellmay be a Downlink Secondary Component Carrier (DL SCC), while in theuplink, it may be an Uplink Secondary Component Carrier (UL SCC). AnSCell may or may not have an uplink carrier.

A cell, comprising a downlink carrier and optionally an uplink carrier,is assigned a physical cell ID and a cell index. A carrier (downlink oruplink) belongs to only one cell, the cell ID or Cell index may alsoidentify the downlink carrier or uplink carrier of the cell (dependingon the context it is used). In the specification, cell ID may be equallyreferred to a carrier ID, and cell index may be referred to carrierindex. In implementation, the physical cell ID or cell index may beassigned to a cell. Cell ID may be determined using the synchronizationsignal transmitted on a downlink carrier. Cell index may be determinedusing RRC messages. For example, when the specification refers to afirst physical cell ID for a first downlink carrier, it may mean thefirst physical cell ID is for a cell comprising the first downlinkcarrier. The same concept may apply to, for example, carrier activation.When the specification indicates that a first carrier is activated, itequally means that the cell comprising the first carrier is activated.

Embodiments may be configured to operate as needed. The disclosedmechanism may be performed when certain criteria are met, for example,in wireless device, base station, radio environment, network, acombination of the above, and/or the like. Example criteria may bebased, at least in part, on for example, traffic load, initial systemset up, packet sizes, traffic characteristics, a combination of theabove, and/or the like. When the one or more criteria are met, theexample embodiments may be applied. Therefore, it may be possible toimplement example embodiments that selectively implement disclosedprotocols.

FIG. 6 shows an example heterogeneous network in an example embodiment.The coverage and capacity of macro base station 601 may be extended bythe utilization of base stations with lower transmit power. Micro, Pico,femto and relay nodes are examples of low power base stations. In anexample embodiment, pico base stations (or pico-cell) 602, 603, and 607may have transmit power ranges from approximately 200 mW toapproximately 5 W. Macro base stations may have a transmit power thattypically varies between 5 and 100 W. Femto base stations (orfemto-cells) may be used for local services such as in indoor services,and their transmit power may be approximately 200 mW or less. These arejust some example power ranges, and as such, should not be considered asa hard limit on the transmit power of a base station type. For example,some femto-cell product may transmit at a power greater than 200 mW.Femto or pico base stations 605, 606 may be configured with a restrictedsubscriber group that may allow access only to its closed subscribergroup (CSG) members. Such femto or pico base stations may be referred toas closed femtos or picos. Femto or pico base stations may also beconfigured as open femtos 604 or picos 602, 603. Relay Nodes (e.g. 608)may employ the macro base stations air interface as a backhaul and mayincrease coverage and capacity of the macro base station. A network thatcomprises of a mix of macro base stations and low-power nodes such aspico or femto base stations, where some base stations may be configuredwith restricted access and some may lack a wired backhaul, is referredto as a heterogeneous network.

Femto cells may be classified as open or closed depending on whether thefemto cells allow access to all, or to a restricted set of wirelessdevices. Closed femtos may restrict the access to a closed subscribergroup (CSG). Open femtos may be similar to pico-cells, but may use thenetwork backhaul provided by the home network. A femto cell may also bea hybrid, whereby many wireless devices may have access, but with lowerpriority for the wireless devices that do not belong to the femto'ssubscriber group. Closed femtos may not allow access to wirelessdevices, and may become a source of interference to those wirelessdevices. Co-channel deployments of closed femtos may cause coverageholes and hence outage of a size proportional to the transmit power ofthe femto-cell. Femto-cells may or may not have an X2 interface.OAM-based or X2 based techniques in conjunction with possibly autonomouspower control techniques may be used for interference management withfemto cells depending on the existence of a femto X2 interface. Thesetechniques may reduce the outage and/or interference that these networknodes cause around them and enable reception of the signal from themacro-cell in close proximity to the closed femto.

Co-channel deployment of low-power nodes and high power nodes mayintroduce new challenges. The introduction of low-power nodes in a macronetwork may create an imbalance between uplink and downlink coverage.Due to the larger transmit power of the macro base station, the handoverboundary may be shifted closer to the low-power node. This shift maylead to severe uplink interference problems as wireless devices servedby macro base stations create strong interference to the low-powernodes. Given the relatively small footprint of low-power nodes,low-power nodes may become underutilized due to geographic changes indata traffic demand. The limited coverage of low-power nodes may be areason for limited performance gain in heterogeneous networks. Some ofthe deployed femto cells may have enforced restricted associations,which may create a coverage hole and may exacerbate the interferenceproblem.

FIG. 7 illustrates a few example interference scenarios in an exampleembodiment. The solid arrow shows the desired signal, and the arrow withthe dashed line shows the unwanted interference. Wireless device 701 maynot be a member of CSG cell 705 and may be roaming in the coverage areaof femto-cell 705. It may receive the signal from macro base station708, and may receive high interference from CSG pico-cell 705. Inanother example, wireless device 702 may not be a member of CSG cell 706and may be roaming in the coverage area of femto-cell 706. The wirelessdevice 702 may transmit a signal to base station 708 in the macro basestation uplink channel. The wireless device 702 may create highinterference for femto-cell 706. The wireless device 703 may not be amember of CSG cell 707 and may be roaming in the coverage area offemto-cell 707. The wireless device 703 may be a member of CSGfemto-cell 706 and may a transmit signal to femto-cell 706. The wirelessdevice 703 may create high interference for femto-cell 707. In anotherexample scenario, the wireless device 704 may be in the cell coverageedge of pico-cell 709. The wireless device 704 may receive a signal frompico-cell 709. The wireless device 704 may also receive highinterference from macro base station 708. As shown in these examples, inorder to cope with the interference, it may be required to introducetechniques that may adequately address these issues.

A new physical layer design in LTE networks may allow for flexible timeand frequency resource partitioning. This added flexibility may enablemacro- and femto/picocells to assign different time-frequency resourceblocks within a carrier or different carriers (if available) to theirrespective wireless devices. This is one of the inter-cell interferencecoordination (ICIC) techniques and may be used on a downlink or anuplink to mitigate interference. With additional complexity, jointprocessing of serving and interfering base station signals may furtherimprove the performance of heterogeneous networks.

According to some of the various aspects of embodiments, cell rangeexpansion through handover biasing and resource partitioning amongdifferent node power classes may decrease interference. The biasingmechanism may allow for load balancing. Depending on the bias value, thenetwork may control the number of wireless devices associated with thelow-power nodes and therefore control traffic demand at those nodes.Resource partitioning, which may be adaptive, may allow configurationand adjustment of interference protected resources, enabling wirelessdevices in a cell's expanded area to receive data. Resource partitioningtechniques may mitigate uplink and downlink interference and allownon-CSG member wireless devices to receive service when in proximity ofclosed femto-base stations.

In a heterogeneous network, the network nodes may be deployed in thesame frequency layer. Deploying low-power nodes at the same frequencylayer as the (high-power) macro-cells may present interference problemsin the case of closed femtos. Also, for the case of open access nodes(open femtos, pico-cells, and RNs), the coverage of the low-power nodesmay be overshadowed by the transmissions of the high-power nodes.Interference coordination techniques may solve these problems. Areduction of closed femto interference to the macro layer and aperformance increase from the introduction of open access low-powernodes may be achieved by interference control techniques. To enableefficient support of co-channel deployment of heterogeneous networks, aninterference management scheme may adapt to different traffic loads anddifferent numbers of low-power nodes at various geographical areas.

According to some of the various aspects of embodiments, resourcepartitioning may be employed for interference management in co-channeldeployments. To reach its full potential, resource partitioning may bepaired with interference-cancellation-capable wireless devices. Similarapproaches may be applied to micro, pico, femto, and relay nodes. Eachnode may have its own caveats. For example, the X2 backhaul link betweenthe macro and relay base stations may be over an LTE air interface. Inanother example, closed femto cells may create their own interferencechallenges. Femto base stations may lack an X2 interface and employstatic or dynamic interference management methods using OAM-based orsimilar solutions.

According to some of the various aspects of embodiments, adaptiveinterference management in LTE may be enabled through X2 backhaulcoordination of resources used for scheduling data traffic. Thegranularity of the negotiated resource may be a subframe. One of thevarious motivations behind resource partitioning may be to controlinterference and/or enable cell range expansion through cell biasing. Ina typical case, cell range expansion may be enabled to improve systemcapacity, and a cell bias may be applied to low-power nodes. The biasvalue may refer to a threshold that triggers a handover between twocells. A positive bias may enable a wireless device to be handed over toa pico-cell when the difference in the signal strength from the macro-and pico-cells drop below a bias value. The high-power node (macro basestation) may inform the low-power node (pico base station) of whichresources may be utilized for scheduling macro wireless device and whichsubframes would remain unutilized (almost blank subframes). Low-powernodes may be made aware of the interference pattern from a high-powerbase station and may schedule a wireless device in the cell extendedareas on subframes protected from high-power interference. That is,subframes corresponding to almost blank subframes at the high-power basestation.

According to some of the various aspects of embodiments, the X2interface may enable direct base station to base station interface forinter-cell interference coordination (ICIC). Co-channel deployments ofheterogeneous networks may require coordination of almost blanksubframes. Almost blank subframes may reduce the interference created bythe transmitting node while providing full legacy support. On almostblank subframes, base station may not schedule unicast traffic while itmay transmit acquisition channels and common reference signal to providelegacy support. FIG. 8 shows an example almost blank subframe. In thisexample CRS (R0, R1, R2, R3 signals) are transmitted only in the controlregion and are not transmitted in the data region. The interfering basestation may still transmit PSS, SSS, PBCH, and RSs to support legacyterminals. Some interference still may exist. In this example, no datamay be transmitted in almost blank subframes or data may be transmittedat a substantially lower power in almost blank subframes.

Interference coordination using almost blank subframes may be performedby means of a bitmap. Each bit in the bitmap may be mapped to a singlesubframe. The size of the bitmap may be, for example, 40 bits, resultingin the interference pattern repeating itself after 40 ms. FIG. 9 showsan example almost blank subframe configuration in an example embodiment.In this example embodiment, no data may be scheduled in almost blanksubframes (ABS). In another embodiment, data may be scheduled in almostblank subframes at a substantially lower power. Subframes 901, 902, 903,and 904 may be configured as ABS in the macro base station. When a macrobase station transmits an almost blank subframe, data may not bescheduled in that subframe (or data may be transmitted at asubstantially lower power). This may increase the coverage of the femtoor pico base stations close to that macro base station. Subframes 905and 906 may be configured as ABS in the femto base station. When thefemto base station transmits an almost blank subframe, data may not bescheduled in that subframe (or data may be transmitted at asubstantially lower power). This may increase coverage allowed for themacro base station or the neighboring femto base stations. In theexample of FIG. 9, the almost blank subframe pattern may be repeatedevery 10 msec. This is just an example and various configurations may bepossible. The almost blank subframe configuration may be changeddynamically according to load and traffic, time of the day, or manyother parameters. In an example embodiment, based on the data trafficdemand, the pattern may change as often as every 40 ms. Thecommunication between nodes may be peer to peer. Or it may be in amaster-slave relationship. The node creating dominant interferenceconditions may control which resources may be used to serve wirelessdevices in the cell range extension area. In an example scenario, amacro base station may be a master, and a pico base station may be aslave since cell range expansion would most frequently be establishedfor pico base stations. The cell range expansion may be desirable for amacro base station as well. A use case for cell range expansion at themacro base station may be to reduce the number of handovers. In ascenario with a large number of high-mobility users, the number ofhandovers in the network may become a problem, for example when in thedeployment of pico base stations the cells become small. The sameresource partitioning schemes may then be utilized to allow highmobility macro wireless devices to remain attached to a macro-cell whiledeep inside coverage of a pico-cell. In this case, the pico base stationmay restrict scheduling data traffic on some resources, allowingcoverage for high-mobility macro wireless devices.

According to some of the various aspects of embodiments, subframeresource partitioning may create an interference pattern that mayrequire a new radio resource measurement paradigm. As dominantinterference may potentially vary from one subframe to the other, inorder to ensure radio resource management measurement accuracy, it maybe needed to restrict measurements to a desired set of subframes. In anexample embodiment, it may be desirable to define anchorinterference-protected resources that may be utilized for radio resourcemeasurement. The 40-bit bitmap may include indications of whichsubframes may have static protection from interference and therefore maybe suitable for measurements. The remaining resources may change moreoften.

According to some of the various aspects of embodiments, the servingbase station may inform a wireless device of the set of subframes towhich the wireless device measurement may be restricted. A set ofsubframes may be configured for radio link monitoring and to check ifthe current connection is reliable enough. The same or a different setof subframes may be introduced for radio resource management, forexample, a handover decision. An additional set of subframes may besignaled for the measurement for some neighboring base stations. Thisconfiguration may be relatively static and may not change rapidly.Another set of subframes may be configured in the wireless device forchannel state information reporting and link adaptation. Two sets ofsubframes may be signaled to a wireless device for two different channelstate information types. For example, one may be for almost blanksubframes, and the other may be for normal subframes. This configurationmay change dynamically depending on the network configuration.

FIG. 10 illustrates example channel state information bitmaps and anexample radio link management bitmap. Subframe 1001 (subframe 3) issemi-statically configured as ABS and therefore it is used for radiolink management in a wireless device in a victim base station. Subframes1002, 1003, and 1004 (subframes 1, 6, and 8) are dynamically configuredas ABS subframes. CSI bitmap 1 is used for a first channel stateinformation measurement and CSI bitmap 2 is used for a second channelstate information measurement. This is an example, and variousconfigurations and bitmap lengths, such as 40 bits or 70 bits, may alsobe supported. When there is no X2 interface, a static OAM-based orsimilar solution may be employed. The same principle of extendingcoverage of one cell into the area covered by the other may be achieved.In this case, it may be the macro-cell service that needs to be extendedinto an area covered by the closed femto-cell.

The resource partitioning may reduce interference from the data channel.Interference from the acquisition channels and CRS signal may remain,since these signals may be transmitted for backward compatibilityreasons. Subframe time shifting may be utilized in FDD systems to reducecollision of the acquisition channels between base stations of differentpower classes that require partitioning, but may not be employed in TDDsystems. Interference mitigation for the acquisition channels may beneeded for cell range expansion to enable the wireless device to detectand acquire a weak cell and then measure and feedback the measurementreport to the network, which may be needed for handover and cell rangeexpansion.

CRS interference mitigation may improve system performance. CRSinterference may degrade turbo code performance and the overallsignal-to-interference-plus-noise radio (SINR). Therefore, the potentialgains of cell range expansion may be reduced. Given that acquisitionchannels and CRS may be broadcast at high power targeting wirelessdevices at the cell edge, a robust wireless device solution is feasible.

One of the various rationales for the wireless device solution for theacquisition signals and CRS interference mitigation is that interferencemay be estimated and subtracted so that in the end it may not representsignificant interference. Acquisition channels may be transmitted at thesame location in cells, which means that the acquisition channelsinterference may comprise acquisition channels from neighboringinterfering cells. This structure may lend itself to a design of aninterference canceller. A wireless device receiver first may decode thestrongest signal, may perform channel gain estimation toward theinterfering cell, may cancel the interfering signal, and may continuethe procedure until acquisition channels of the serving cell areacquired.

A similar procedure may be performed to remove CRS interference. Thedifference may be that CRS tones may also interfere with data tonessince interference between CRS tones between high-power and low-powernodes may be reduced by CRS tone shifting. The procedure may be similar.If strong CRS interference is detected, and after the channel gaintoward the interfering cell is estimated, the CRS signal may becancelled. The procedure may be repeated until interfering signals aresubtracted.

RRC messages are used to configure wireless device configurationparameters related to almost blank configuration and measurements. Anexample RRC message configuration in an example embodiment is describedin the following paragraphs. A subframe pattern bitmap may indicate thetime domain measurement resource restriction pattern for primary orsecondary carrier measurements (RSRP, RSRQ and the radio linkmonitoring). The bitmap length may be, for example, 40 bits. Anothersubframe bitmap may configure neighbor measurement patterns. A neighbormeasurement bitmap along with the list of cells for which the neighbormeasurement bitmap is applied may be transmitted to the wireless device.If the list of cells is not included, the wireless device may apply timedomain measurement resource restrictions for neighbor cells. Time domainmeasurement resource restriction patterns may be applicable to neighborcell RSRP and RSRQ measurements on a carrier frequency indicated by RRC.In an example embodiment, two CSI subframe pattern configuration bitmapsmay be transmitted to the wireless device. Each bit map may be 40 bitslong. The CSI configuration may include a channel quality index, a rankindicator, a precoding matrix indicator, a combination thereof, or thelike.

A base station may broadcast an ABS subframe configuration employingMBSFN (multi-cast, broadcast, single frequency network) subframeconfiguration broadcast or unicast messages. An example broadcastmessage is an RRC system information block. MBSFN or ABS subframeconfigurations may include a radio frame allocation period, a radioframe allocation offset, a subframe allocation bitmap, any combinationof these parameters, or the like. A radio frame allocation period may be1, 2, 4, 8, 16 or 32 frames. A radio frame allocation offset may be anumber between 1 to 7 subframes. A subframe allocation bitmap may be forone frame or four frames. Radio frames that contain MBSFN/ABS subframesmay occur when equation (SFN mod radio Frame Allocation Period=radioFrame Allocation Offset) is satisfied. Values 1 and 2 may not beapplicable to radio frame allocation period when four Frames are used.

According to some of the various aspects of embodiments, a subframeallocation bitmap may define the subframes that are allocated for MBSFNwithin the radio frame allocation period defined by the radio frameallocation period and the radio frame allocation offset. A subframeallocation bitmap for one frame may be six bits long and for four framesmay be 24 bits long. In a bit-map indicating MBSFN/ABS subframeallocation in four consecutive radio frames, a “1” may denote that thecorresponding subframe is allocated for MBSFN/ABS. The bitmap may beinterpreted as follows: For FDD: Starting from the first radio frame andfrom the first/leftmost bit in the bitmap, the allocation may apply tosubframes #1, #2, #3, #6, #7, and #8 in the sequence of the fourradio-frames. For TDD: Starting from the first radio frame and from thefirst/leftmost bit in the bitmap, the allocation applies to subframes#3, #4, #7, #8, and #9 in the sequence of the four radio-frames. Thelast four bits may not be used. Uplink subframes may not be allocated.

Other example configurations may be implemented. For example, an MBSFNsubframe configuration may be used to introduce ABS subframes andsubframes used for scheduling release 10 or above wireless devices. Forexample, an MBSFN configuration may introduce subframe 1, 3, 6 and 8 asMBSFN subframes in a frame. Then MBSFN subframe 1 may be used forscheduling release 10 or above wireless devices, and MBSFN subframe 3,6, and 8 may be used as almost blank subframes. Therefore, as seen inthis example, MBSFN configuration may indicate other types of subframesin addition to almost blank subframes. In another configuration, a basestation may use one or many of MBSFN subframes for broadcasting ormulticasting services. In a typical scenario, in which MBSFN may beconfigured, for example, for four frames, with a period of 40 msec,various configurations for combining ABS, MBSFN, and release 10 or abovesubframes may be possible. In this specification, ABS subframes may becalled special subframes.

According to some of the various aspects of embodiments, specialsubframes may be configured for the primary carrier (cell) as well asone or more secondary carriers (cells). The configuration parameters forthe measurement parameters of the secondary carrier(s) may employ thebitmaps with the same length and format of the configuration parametersof the primary carrier. In an example embodiment, the configurationparameters of special subframes for one or more secondary carriers maybe the same as the configuration parameters for the special subframeconfiguration of the primary carrier.

According to some of the various aspects of embodiments, non-backwardcompatible carriers may be configured with special subframes. In anon-backward compatible carrier special subframe, no common referencesignal may be transmitted during the special subframe. Or, data andreference signals in a non-backward compatible carrier special subframemay be transmitted at a substantially lower power to ensure that nointerference (to other cells) is observed during the special subframe.

Example embodiments of the invention may enable detection of controlchannels in wireless communication systems. Other example embodimentsmay comprise a non-transitory tangible computer readable mediacomprising instructions executable by one or more processors to causedetection of control channels in wireless communication systems. Yetother example embodiments may comprise an article of manufacture thatcomprises a non-transitory tangible computer readable machine-accessiblemedium having instructions encoded thereon for enabling programmablehardware to cause a device (e.g. wireless communicator, UE, basestation, etc.) to enable detection of control channels. The device mayinclude processors, memory, interfaces, and/or the like. Other exampleembodiments may comprise communication networks comprising devices suchas base stations, wireless devices (or user equipment: UE), servers,switches, antennas, and/or the like.

Co-channel deployments may be of interest due to cost effectiveness andhigh spectral efficiency. Resource partitioning may effectively mitigateinterference from the data channel. However, interference from theacquisition channels, CRS signal, and control channels (including acontrol format indicator channel) may remain, since these signals may beneeded to be transmitted for backward compatibility reasons. Subframetime shifting may be utilized in FDD systems to avoid collision of theacquisition channels between base stations of different power classesthat require partitioning. Subframe time shifting may not be necessaryin TDD systems. There may be limited network solutions for CRSinterference mitigation for either FDD or TDD systems. Withoutadditional interference mitigation of the acquisition channels, CRS, andcontrol channels (including the control format indicator channel),limited medium bias values (for example, 6-10 dB) for handover may besupported. This may limit the potential for cell range expansion.

Interference mitigation for the acquisition channels may be needed forcell range expansion. Interference mitigation may enable wirelessdevices to detect and acquire a weak cell and then measure and feedbackthe measurement report to the network.

CRS interference mitigation may have a role in system performance.Strong CRS interference, even though present on a relatively smallfraction of resource elements, may degrade turbo code performance andthe overall signal-to-interference-plus-noise ratio (SINR). Thepotential gains of cell range expansion may be reduced. The controlformat indicator channel may carry important information without whichthe wireless device may not be able to decode the control information.Strong interference on the control format indicator channel may resultin loss of information carried on this channel and may cause a wirelessdevice to lose the ability to decode other control channels carryingscheduling and other related information.

According to some of the various aspects of embodiments, a wirelessdevice solution may be feasible given that acquisition channels, CRS,and/or the control format indicator channel may be broadcast at a highpower targeting wireless devices at the cell edge. Interference may beestimated and subtracted so that it may not represent significantinterference for the acquisition signals, CRS, and the control formatindicator channel. Acquisition channels may be transmitted at the sameradio resource location in cells. The acquisition channels interferencemay comprise the acquisition channels from the neighboring interferingcells. This structure may lend itself to a design of an interferencecanceller. A wireless device receiver may first decode one of thestrongest signals, may perform channel gain estimation toward theinterfering cell, may cancel the interfering signal, and may continuethe procedure until acquisition channels of the serving cell areacquired.

A similar procedure may be performed to remove CRS interference. The CRStones may also interfere with data tones since interference between CRStones between high- and low-power nodes may be avoided/reduced by CRStone shifting. If strong CRS interference is detected, and after thechannel gain toward the interfering cell is estimated, the CRS signalmay be cancelled. The procedure may be repeated until interferingsignals are subtracted.

According to some of the various aspects of embodiments, the controlformat indicator channel may be transmitted at the same location incells. The control format indicator channel's interference may comprisethe control format indicator channel from the neighboring interferingcells. This structure may lend itself to a design of an interferencecanceller. A wireless device receiver may first decode one of thestrongest signals, may perform channel gain estimation toward theinterfering cell, may cancel the interfering signal, and may continuethe procedure until the control format indicator channel of the servingcell is decoded. There is a need to develop mechanisms for processingbroadcast channels, for example, in hierarchical networks. A differentsignal processing mechanism may be needed compared with traditionalmethods when there is strong co-channel interference among basestations. The mechanisms may be different than traditional methods sincethe signal patterns may be known or the wireless device may able todetermine interference patterns before an interference cancellationprocess starts. Embodiments of the present invention provide mechanismsto process received signals and to obtain broadcast messages andsignals.

In an example embodiment, resource partitioning mechanisms such as ABSsubframe configurations may be used for data channels. Differentinterfering signals may be transmitted at different times employing anABS configuration among interfering base stations. In an exampleembodiment, resource partitioning may be performed in frequency domains,for example different interfering ePDCCH and/or PDCCH may be transmittedin different frequency bands. Simulation results show that advancedinterference cancellation may be effective on control format indicatorchannel and/or physical broadcast channels, while the same techniquesmay not be applicable to other channels such as (e)PDCCH and/or PDSCH.Signal pattern may have more limited possibilities for control formatindicator channel and/or physical broadcast channels. The number ofiterations required for interference cancellation for control formatindicator channel and physical broadcast channels may be limited. Atleast for the above reasons, interference cancellation is applied tocontrol format indicator channel and/or physical broadcast channels.

The same or similar approaches may not be appropriate for all controlchannels, (e.g., control channels carrying scheduling information)and/or data channels. The reason may be that such control and/or datachannels may be scrambled with the identity of a target wireless device,and in order for a wireless device to cancel the interference of suchchannels, the wireless device may need to try a very large number ofhypotheses considering the information being transmitted to potentialwireless identifiers in the neighboring cell. This may require a largeamount of computational complexity, and may not be practical. Theinterference cancellation for synchronization signals may require alimited number of correlations to detect interfering synchronizationsignal. This process may be simpler than interference cancellation for(e)PDCCH and/or PDSCH. I mechanism is introduced for interferencecancellation of synchronization signal.

FIG. 11 is a flow chart illustrating an example processing of controlformat indicator signal as per an aspect of an embodiment of the presentinvention. According to some of the various aspects of embodiments, awireless device may demodulate, descramble and decode a first controlformat indicator signal to generate a first signal as shown in 1102. Thefirst control format indicator signal may be received from a first basestation on a plurality of OFDM subcarriers in a first OFDM symbol of afirst subframe in a plurality of subframes. The wireless device mayprocess the first signal. The processing of the first signal maycomprise encoding, scrambling, modulating and scaling the first signalas shown in 1104. The wireless device may subtract the processed firstsignal from received signals on the plurality of OFDM subcarriers in thefirst OFDM symbol of the first subframe to generate a second signal asshown in 1106. The wireless device may process the second signal. Theprocessing of the second signal may comprise demodulating, descramblingand decoding a second control format indicator signal to generate asecond control format indicator as shown in 1108. The second controlformat indicator signal may be received from a second base station inthe first OFDM symbol of the first subframe. The wireless device maydetermine the number of OFDM symbols of a control region of the secondbase station based on the second control format indicator as shown in1110.

According to some of the various aspects of embodiments, the second basestation may be of a different base station type than the first basestation. The first base station type may be one of the following: amacro base station type, a pico base station type, a femto base stationtype with open access, and a femto base station type with closesubscriber group access. The second base station type may be one of thefollowing: a macro base station type, a pico base station type, a femtobase station type with open access, and a femto base station type withclose subscriber group access. The second control format indicator maycomprise two bits of information. The second control format indicatorsignal may be encoded, by the second base station, employing arepetition code. The first control format indicator signal may bereceived over sixteen modulation symbols. Those skilled in the art willrecognize that the first control format indicator signal may be receivedover different amount of modulation symbols in accordance with varioussystems.

FIG. 12 is a flow chart illustrating an example processing of physicalbroadcast signal as per an aspect of an embodiment of the presentinvention. According to some of the various aspects of embodiments, awireless device may demodulate, descramble and decode a first physicalbroadcast signal to generate a first signal as shown in 1202. The firstphysical broadcast signal may be received from a first base station on aplurality of OFDM subcarriers substantially in the center of a frequencyband of a carrier in a plurality of OFDM symbols of a subset ofsubframes in a plurality of subframes. The term substantially is used toindicate possible inaccuracies in the frequency of frequencysynthesizers. The signal is practically considered in the center of thefrequency band. The wireless device may process the first signal. Theprocessing of the first signal may comprise encoding, scrambling,modulating and scaling the first signal as shown in 1204. The wirelessdevice may subtract the processed first signal from received signals onthe plurality of OFDM subcarriers in the plurality of OFDM symbols ofthe subset of subframes to generate a second signal as shown in 1206.The wireless device may process the second signal. The processing of thesecond signal comprising demodulating, descrambling and decoding asecond physical broadcast signal to generate a second physical broadcastmessage as shown in 1208. The second physical broadcast signal may bereceived from a second base station in the plurality of OFDM symbols ofthe subset of subframes. The wireless device may determine a pluralityof system parameters of the second base station based on the secondphysical broadcast message as shown in 1210.

According to some of the various aspects of embodiments, the second basestation may be of a different base station type than the first basestation. The first base station type may be one of the following: amacro base station type, a pico base station type, a femto base stationtype with open access, and a femto base station type with closesubscriber group access. The second base station type may be one of thefollowing: a macro base station type, a pico base station type, a femtobase station type with open access, and a femto base station type withclose subscriber group access. The first physical broadcast signalreception may reoccur periodically with a fix period, for example every40 msec. The first physical broadcast signal may be received overseventy two OFDM subcarriers substantially in the center of a carrier.The plurality of system parameters may comprise at least one of: systembandwidth information, HARQ indicator channel structure information, andeight most significant bits of system frame number. The second physicalbroadcast signal may be encoded, by the second base station, employing aconvolutional code and a repetition code. Those skilled in the art willrecognize that physical broadcast signal(s) may be encoded using othertechniques. The second physical broadcast message may comprise fourteenbits of information. The second physical broadcast message may comprisea master information block.

According to some of the various aspects of embodiments, a wirelessdevice may correlate received signals on a first plurality of OFDMsubcarriers substantially in the center of a frequency band of a carrierin a first subset of OFDM symbols with a first plurality ofpredetermined primary synchronization signals to produce a firstplurality of correlation values. In one example embodiment, thecorrelation process may comprise a summation of a plurality ofmultiplications. In another example implementation, correlation may beperformed by hardware, firmware, software in combination with hardware,and/or an electronic circuit, for example, by a matched filter, DSPprocessor and/or the like. Other examples of correlation mechanisms maybe implemented. Correlation may be of any type of correlation and maynot be limited to above embodiments. Correlation process may be any typeof mechanisms that detects association, similarity, connection, and/orrelationship between two signals.

The wireless device may identify based at least in part on the firstplurality of correlation values, a first primary synchronization signalin the first plurality of predetermined primary synchronization signalsas a primary synchronization signal transmitted by a first base station.The wireless device may process the first primary synchronizationsignal. The processing of the first primary synchronization signal maycomprise scaling the first primary synchronization signal by a scalingfactor that depends, at least in part, on a correlation valuecorresponding to the first primary synchronization signal. The wirelessdevice may subtract the processed first primary synchronization signalfrom received signals on the first plurality of OFDM subcarriers in thefirst subset of OFDM symbols to generate a first updated receivedsignal. The wireless device may correlate the first updated receivedsignal with a second plurality of predetermined primary synchronizationsignals to produce a second plurality of correlation values. Thewireless device may identify based at least in part on the secondplurality of correlation values, a second primary synchronization signalas a primary synchronization signal transmitted by a second basestation.

The wireless device may correlate received signals on a second pluralityof OFDM subcarriers substantially in the center of the frequency band ofthe carrier in a second subset of OFDM symbols with a first plurality ofpredetermined secondary synchronization signals to produce a thirdplurality of correlation values. The wireless device may identify basedat least in part on the third plurality of correlation values, a firstsecondary synchronization signal in the first plurality of predeterminedsecondary synchronization signals as a secondary synchronization signaltransmitted by the first base station. The wireless device may processthe first secondary synchronization signal. The processing of the firstsecondary synchronization signal may comprise scaling by a scalingfactor that depends, at least in part, on a correlation valuecorresponding to the first secondary synchronization signal.

The wireless device may subtract the processed first secondarysynchronization signal from received signals on the second plurality ofOFDM subcarriers in the second subset of OFDM symbols to generate asecond updated received signal. The wireless device may correlate thesecond updated received signal with a second plurality of predeterminedsecondary synchronization signals to produce a fourth plurality ofcorrelation values. The wireless device may identify based at least inpart on the fourth plurality of correlation values, a second secondarysynchronization signal in the second plurality of predeterminedsecondary synchronization signals as a secondary synchronization signaltransmitted by the second base station. The wireless device may obtainframe and subframe timing information of the second base stationemploying the second primary synchronization signal and the secondsecondary synchronization signal.

According to some of the various aspects of embodiments, the firstprimary synchronization signal may have a highest correlation valueamong the first plurality of correlation values. The second primarysynchronization signal may have a highest correlation value among thesecond plurality of correlation values. The first secondarysynchronization signal may have a highest correlation value among thethird plurality of correlation values. The second secondarysynchronization signal may have a highest correlation value among thefourth plurality of correlation values. The first plurality ofpredetermined secondary synchronization signals may depend, at least inpart, on the first primary synchronization signal. The second pluralityof predetermined secondary synchronization signals may depend, at leastin part, on the second primary synchronization signal.

FIG. 13 is a flow chart illustrating an example processing ofsynchronization signal as per an aspect of an embodiment of the presentinvention. According to some of the various aspects of embodiments, awireless device may correlate received signals on a plurality of OFDMsubcarriers substantially in the center of a frequency band of a carrierin a subset of OFDM symbols with a first plurality of predeterminedsynchronization signals to produce a first plurality of correlationvalues as shown in 1302. The wireless device may identify based at leastin part on the first plurality of correlation values, a firstsynchronization signal in the first plurality of predeterminedsynchronization signals as a synchronization signal transmitted by afirst base station as shown in 1304. The wireless device may process thefirst synchronization signal. The processing of the firstsynchronization signal may comprise scaling the first synchronizationsignal by a scaling factor that depends, at least in part, on acorrelation value corresponding to the first synchronization signal asshown in 1306. The wireless device may subtract the processed firstsynchronization signal from received signals on the plurality of OFDMsubcarriers in the subset of OFDM symbols to generate an updatedreceived signal as shown in 1308. The wireless device may correlate theupdated received signal with a second plurality of predeterminedsynchronization signals to produce a second plurality of correlationvalues as shown in 1310. The wireless device may identify based at leastin part on the second plurality of correlation values, a secondsynchronization signal as a synchronization signal transmitted by asecond base station as shown in 1312. The wireless device may obtainframe and subframe timing information of the second base stationemploying the second synchronization signal as shown in 1314.

The first base station type may be of a different type than the secondbase station type. The first base station type may be one of thefollowing: a macro base station type, a pico base station type, a femtobase station type with open access, and a femto base station type withclose subscriber group access. The second base station type may be oneof the following: macro base station type, a pico base station type, afemto base station type with open access, and a femto base station typewith close subscriber group access.

The first synchronization signal may have a highest correlation valueamong the first plurality of correlation values. The secondsynchronization signal may have a highest correlation value among thesecond plurality of correlation values. The plurality of synchronizationsignals may be transmitted over seventy-two OFDM subcarrierssubstantially in the center of the carrier. The plurality ofsynchronization signals may determine a physical identifier of a carrieron which the plurality of synchronization signals are transmitted. Thescaling factor may be a function of characteristics of a wirelesschannel over which the plurality of synchronization signals aretransmitted.

A similar procedure may be performed to remove CRS interference. The CRStones may also interfere with data tones since interference between CRStones between high- and low-power nodes may be avoided by CRS toneshifting. If strong CRS interference is detected, and after the channelgain toward the interfering cell is estimated, the CRS signal may becancelled. The procedure may be repeated until most of the interferingsignals are subtracted. However, the problem of reliable channel qualityinformation (CQI) feedback for data transmission may remain, dependingon whether CRS tones interfere with data tones or not, and whether theinterfering base station transmits or does not transmit data on thecorresponding subframe (e.g., whether the corresponding subframe is analmost blank subframe for the interfering base station or not). Based onthese alternatives, at least four different cases may be considered forCQI computation:

1. CRS tones of the interfering base station may overlap with the CRStones of the interfered base station, and the interfering base stationtransmits data on the corresponding subframe. In this case, there may beno need for post processing of the interference values estimated on theCRS tones. The interference seen on the data tones may most likely besimilar to the interference seen on the CRS tones. The wireless devicemay use the interference estimate obtained from the CRS tones directlywith the channel estimates obtained for the serving base station fromthe CRS tones to compute the CQI value and may feed it back to itsserving base station.

2. CRS tones of the interfering base station may overlap with CRS tonesof the interfered base station, but the interfering base station may nottransmit data on the corresponding subframe (e.g., the correspondingsubframe is an almost blank subframe of the interfering base station).In this case, the interference estimated on the CRS tones may includeinterference from the interfering base station, but this interferencemay not be present on the data tones. So the interference value may beoverestimated. The wireless device may separately estimate theinterference contribution of the interfering base station, and maysubtract it from the total interference measured on the CRS tones toobtain a more accurate estimate of the interference observed on the datatones. This more accurate interference estimate may be used along withthe channel estimate of the serving base station obtained from the CRStones to compute the CQI value.

3. CRS tones of the interfering base station may not overlap with CRStones of the interfered base station, and the interfering base stationtransmits data on the corresponding subframe. In this case, depending onthe signals transmitted by the interfering base station on the CRS tonesof the interfered base station, there may be at least two options. Ifthe interfering base station punctures these tones and does not transmita signal on these tones (to allow for more accurate channel estimationat the interfered base station), then the interference value estimatedon the CRS tones may be an underestimate and may need to be adjustedbefore using the interference value estimate in a CQI computation. Thisadjustment may involve separate estimation of the potential interferencefrom the interfering base station and adding the separate estimation tothe total interference estimated on the CRS tones of the interfered basestation. If on the other hand, the interfering base station transmitsdata on the CRS tones of the interfered base station, then theinterference estimate on the CRS tones of the interfered base stationmay be accurate and there may be no need for further adjustment for theCQI computation.

4. CRS tones of the interfering base station may not overlap with CRStones of the interfered base station, and the interfering base stationmay not transmit data on the corresponding subframe. In this case, theremay be no underestimation or overestimation of the interference on theCRS tones of the interfered base station. Therefore, there may be noneed for further adjustment for the CQI computation.

FIG. 14 is a flow chart illustrating an example processing of referencesignals as per an aspect of an embodiment of the present invention. Awireless device may receive a first reference signal from a first basestation in the plurality of base stations on a first plurality of OFDMresources in a first subframe in the plurality of subframes as shown in1402. The first plurality of OFDM resources may depend, at least inpart, on a first base station identifier of the first base station. Thewireless device may estimate a first signal strength corresponding tothe first base station based on the received first reference signal asshown in 1404.

The wireless device may receive a second reference signal from a secondbase station, on a second plurality of OFDM resources in the firstsubframe as shown in 1406. The second plurality of OFDM resources maydepend, at least in part, on a second base station identifier of thesecond base station. The wireless device may estimate a second signalstrength corresponding to the second base station based on the receivedsecond reference signal as shown in 1408. The wireless device mayestimate an interference value on the second plurality of OFDM resourcesbased, at least in part, on the second reference signal as shown in1410. The wireless device may calculate a signal to interference ratiovalue based on the second signal strength and a total interference valueas shown in 1412. If the first plurality of OFDM resources overlap withthe second plurality of OFDM resources, the total interference value maybe computed based upon the interference value. If the first plurality ofOFDM resources do not overlap with the second plurality of OFDMresources, the total interference value may be computed based upon theinterference value plus the first signal strength.

According to some of the various aspects of embodiments, the wirelessdevice may receive a first reference signal from a first base station inthe plurality of base stations on a first plurality of OFDM resources ina first subframe in the plurality of subframes. The first plurality ofOFDM resources may depend, at least in part, on a first base stationidentifier of the first base station. The wireless device may estimate afirst signal strength corresponding to the first base station based onthe received first reference signal. The wireless device may receive asecond reference signal from a second base station in the plurality ofbase stations, on a second plurality of OFDM resources in the firstsubframe. The second plurality of OFDM resources depend, at least inpart, on a second base station identifier of the second base station.The wireless device may estimate a second signal strength correspondingto the second base station based on the received second referencesignal.

The wireless device may estimate an interference value on the secondplurality of OFDM resources based, at least in part, on the secondreference signal. The wireless device may estimate a signal tointerference ratio value based on the second signal strength and a totalinterference value. If the first plurality of OFDM resources do notoverlap with the second plurality of OFDM resources, the totalinterference value may be computed based upon the interference value. Ifthe first plurality of OFDM resources overlap with the second pluralityof OFDM resources, the total interference value may be computed basedupon the interference value minus the first signal strength.

According to some of the various aspects of embodiments, the first basestation may transmit data to a plurality of wireless devices on thefirst subframe. The first base station may not transmit data on thefirst subframe. The first base station may transmit radio signals at asubstantially higher power than the second base station. The second basestation may transmit radio signals at a substantially higher power thanthe first base station. The first base station may be a macro basestation. The first base station may be a pico base station. The firstbase station may be a femto base station with open access. The firstbase station may be a femto base station with close subscriber groupaccess. The second base station may be a macro base station. The secondbase station may be a pico base station. The second base station may bea femto base station with open access. The second base station may be afemto base station with close subscriber group access.

The first reference signal may be a common reference signal. The secondreference signal may be a common reference signal. The first referencesignal may be a channel state information reference signal. The secondreference signal may be a channel state information reference signal.The first signal strength may be a short term signal strength valueobtained from the most recent observation. The first signal strength maybe a long term signal strength value obtained from averaging a pluralityof recent observations. The second signal strength may be a short termsignal strength value obtained from the most recent observation. Thesecond signal strength may be a long term signal strength value obtainedfrom averaging a plurality of recent observations. The interferencevalue may be a short term interference value obtained from the mostrecent observation. The interference value may be a long terminterference value obtained from averaging a plurality of recentobservations.

The control format indicator channel may be transmitted at the samelocation in cells, which means that the control format indicatorchannel's interference may comprise the control format indicator channelfrom the neighboring interfering cells. This structure may lend itselfto a design of an interference canceller. A wireless device receiver mayfirst decode one of the strongest signals, may perform channel gainestimation toward the interfering cell, may cancel the interferingsignal, and may continue the procedure until control format indicatorchannel of the serving cell is decoded.

The same or similar approaches may not be appropriate for other controlchannels, (e.g., control channels carrying scheduling information). Thereason may be that such control channels may be scrambled with theidentity of a target wireless device, and in order for a wireless deviceto cancel the interference of such channels, the wireless device mayneed to try a very large number of hypotheses considering theinformation being transmitted to potential wireless identifiers in theneighboring cell. This may require a large amount of computationalcomplexity, and may not be practical.

The control region of most packet switched technologies may be a sharedregion in the sense that control information for many different wirelessdevices may be transmitted on the same resources. This may reduce theamount of overhead for such systems, especially with dynamic schedulingof the wireless devices, in which, in a given subframe, a small numberof active wireless devices may be scheduled. Each wireless device maymonitor a portion or the entire control region for potential controlchannel transmissions targeting that particular wireless device. On theother hand, many technologies may use a mechanism such as a hashingmechanism to limit the number of the decode hypotheses of the wirelessdevices. As a very simple example, it may be specified that wirelessdevices with the wireless device identifier from the first half of theentire wireless device identifiers space may expect control informationon the first half of the resources of entire the control region, andwireless devices with the wireless device identifier from the secondhalf of the entire wireless device identifiers space may expect controlinformation on the second half of the resources of entire the controlregion. With this rule, the number of decode hypotheses of any wirelessdevice in the system may be reduced by half. Practical systems andtechnologies may use more sophisticated hashing mechanisms to furtherreduce the number of decode hypotheses of the wireless devices.

Following the example given above, an alternate method of mitigatingcontrol channel information which is based on base station coordinationand may not require wireless device involvement or may reduce wirelessdevice involvement may be considered. In this alternate method, basestations that are potential interferers to each other may decide tocoordinate the wireless device identifiers that they assigned to theirserved wireless devices such that the corresponding controltransmissions of the two base stations may not overlap in time frequencyresources or may have a reduced overlap in time frequency resources. Forthe simple example provided above, it may be necessary for the two basestations to agree that one of them uses the first half of the wirelessidentifiers space and the other base station uses the second half of thewireless identifiers space. With this agreement, the controltransmissions of the first base station may take place on the first halfof the resources of the control region and the control transmissions ofthe second base station may take place on the second half of theresources of the control region. This may avoid or reduce overlap andthus reduce interference between each of the base stations.

Practical systems may use more sophisticated hashing algorithms for themapping between wireless device identifiers and control regionresources. Nevertheless, wireless device identifier partitioningalgorithms similar to the scheme described above may be devised so thatwireless device identifier space may be partitioned such that the amountof interfering control resources between base stations may be reduced.

FIG. 15 is a flow chart illustrating transmission of control messages asper an aspect of an embodiment of the present invention. A first basestation may be configured with a first plurality of wireless deviceidentifiers. A second base station may be configured with a secondplurality of wireless device identifiers. For example, a first pluralityof wireless device identifiers may be selected and then assigned to afirst base station, and a second plurality of wireless deviceidentifiers may be selected and then assigned to a second base station.In an example implementation, the selection and/or assignment ofwireless device identifiers to the base stations may be done by anetwork administrator, network management system, and/or the like. Thelist of selected wireless device identifiers may be communicated to thebase station via a management interface. A base station assigns awireless device identifier from the pool of wireless device identifiersconfigured in that base station to wireless device identifiers connectedto the base station.

A first base station may assign a first plurality of wireless deviceidentifiers to a first plurality of wireless devices in connected modeas shown in 1502. The first base station may transmit a plurality offirst unicast and/or broadcast control messages to a first subset of thefirst plurality of wireless devices employing a first plurality of OFDMresources in a first subframe of the first base station as shown in1504. The first plurality of OFDM resources may depend, at least inpart, on wireless device identifiers of the first subset of the firstplurality of wireless devices.

A second base station may assign a second plurality of wireless deviceidentifiers to a second plurality of wireless devices in connected modeas shown in 1506. The second base station may transmit a secondplurality of unicast and/or broadcast control messages to a secondsubset of the second plurality of wireless devices employing a secondplurality of OFDM resources in a second subframe of the second basestation as shown in 1508. The second subframe being transmittedsubstantially simultaneously with the first subframe. The base stationsframe and subframe transmission may be synchronized by GPS, packet basedsynchronization mechanisms, and/or the like. Synchronization errors maybe inevitable due to inaccuracy in the synchronization techniques usedto achieve synchronization among base stations. Synchronization errorsmay be below a small fraction of subframe duration. The second pluralityof OFDM resources may depend, at least in part, on wireless deviceidentifiers of the second subset of the second plurality of wirelessdevices. The first plurality of wireless device identifiers and thesecond plurality of wireless device identifiers may be configured tomaintain overlap between the first plurality of OFDM resources and thesecond plurality of OFDM resources is at or below a pre-determinedthreshold as shown in 1510. In an example embodiment, average overlapover a plurality of subframes may be at or below a threshold. In anotherexample embodiment for most (for example above a pre-determinedpercentage) of subframes, the overlap may be at or below a threshold. Inan example embodiment, overall overlap between OFDM resources of thecontrol regions of the base stations may be reduced to reduceinterference in the control region. For example, the reduction inoverlap could be on each individual frame, or could be a statisticalreduction of overlap over a plurality of frames. Other embodiments toreduce overall overlap may be implemented.

The first base station may be of a different base station type than thesecond base station. The pre-determined threshold is zero or larger. Insome example embodiments, the pre-determined threshold could be one ofthe following: below ten percent of the smaller of the first pluralityof OFDM resources and the second plurality of OFDM resources, belowtwenty percent of the smaller of the first plurality of OFDM resourcesand the second plurality of OFDM resources, or below fifty percent ofthe smaller of the first plurality of OFDM resources and the secondplurality of OFDM resources. In other words, the pre-determinedthreshold may be between ten to fifty percent of the smaller of saidfirst plurality of OFDM resources and said second plurality of OFDMresources. However, those skilled in the art will recognize that otherthreshold values may be employed accordingly depending upon theconstraints of any particular embodiment.

At least one unicast message in the first plurality of unicast controlmessages and the second plurality of unicast control messages maycomprise at least one of the following: a resource identifier, amodulation and coding format indicator, a HARQ process identifier, aredundancy version, a transmission mode indicator, and an uplink powercontrol indicator. The transmission mode indicator may be employed, by awireless device, to determine a transmission mode from a plurality oftransmission modes. The plurality of transmission modes may be one of: atransmit diversity mode, a cyclic delay diversity mode, a spatialmultiplexing mode, a beamforming mode, and a precoding mode. The uplinkpower control command may be an absolute power control command and arelative power control command. The uplink power control indicator maybe a single power control command for a single wireless device. Theuplink power control indicator may comprise a plurality of power controlcommands for a plurality of wireless devices. At least one power controlcommand in the plurality of power control commands may be an absolutepower control command or a relative power control command.

According to some of the various aspects of embodiments, the packets inthe downlink may be transmitted via downlink physical channels. Thecarrying packets in the uplink may be transmitted via uplink physicalchannels. The baseband data representing a downlink physical channel maybe defined in terms of at least one of the following actions: scramblingof coded bits in codewords to be transmitted on a physical channel;modulation of scrambled bits to generate complex-valued modulationsymbols; mapping of the complex-valued modulation symbols onto one orseveral transmission layers; precoding of the complex-valued modulationsymbols on layer(s) for transmission on the antenna port(s); mapping ofcomplex-valued modulation symbols for antenna port(s) to resourceelements; and/or generation of complex-valued time-domain OFDM signal(s)for antenna port(s).

Codeword, transmitted on the physical channel in one subframe, may bescrambled prior to modulation, resulting in a block of scrambled bits.The scrambling sequence generator may be initialized at the start ofsubframe(s). Codeword(s) may be modulated using QPSK, 16QAM, 64QAM,128QAM, and/or the like resulting in a block of complex-valuedmodulation symbols. The complex-valued modulation symbols for codewordsto be transmitted may be mapped onto one or several layers. Fortransmission on a single antenna port, a single layer may be used. Forspatial multiplexing, the number of layers may be less than or equal tothe number of antenna port(s) used for transmission of the physicalchannel. The case of a single codeword mapped to multiple layers may beapplicable when the number of cell-specific reference signals is four orwhen the number of UE-specific reference signals is two or larger. Fortransmit diversity, there may be one codeword and the number of layersmay be equal to the number of antenna port(s) used for transmission ofthe physical channel.

The precoder may receive a block of vectors from the layer mapping andgenerate a block of vectors to be mapped onto resources on the antennaport(s). Precoding for spatial multiplexing using antenna port(s) withcell-specific reference signals may be used in combination with layermapping for spatial multiplexing. Spatial multiplexing may support twoor four antenna ports and the set of antenna ports used may be {0,1} or{0, 1, 2, 3}. Precoding for transmit diversity may be used incombination with layer mapping for transmit diversity. The precodingoperation for transmit diversity may be defined for two and four antennaports. Precoding for spatial multiplexing using antenna ports withUE-specific reference signals may also, for example, be used incombination with layer mapping for spatial multiplexing. Spatialmultiplexing using antenna ports with UE-specific reference signals maysupport up to eight antenna ports. Reference signals may be pre-definedsignals that may be used by the receiver for decoding the receivedphysical signal, estimating the channel state, and/or other purposes.

For antenna port(s) used for transmission of the physical channel, theblock of complex-valued symbols may be mapped in sequence to resourceelements. In resource blocks in which UE-specific reference signals arenot transmitted the PDSCH may be transmitted on the same set of antennaports as the physical broadcast channel in the downlink (PBCH). Inresource blocks in which UE-specific reference signals are transmitted,the PDSCH may be transmitted, for example, on antenna port(s) {5, {7},{8}, or {7, 8, . . . , v+6}, where v is the number of layers used fortransmission of the PDSCH.

Common reference signal(s) may be transmitted in physical antennaport(s). Common reference signal(s) may be cell-specific referencesignal(s) (RS) used for demodulation and/or measurement purposes.Channel estimation accuracy using common reference signal(s) may bereasonable for demodulation (high RS density). Common referencesignal(s) may be defined for LTE technologies, LTE-advancedtechnologies, and/or the like. Demodulation reference signal(s) may betransmitted in virtual antenna port(s) (i.e., layer or stream). Channelestimation accuracy using demodulation reference signal(s) may bereasonable within allocated time/frequency resources. Demodulationreference signal(s) may be defined for LTE-advanced technology and maynot be applicable to LTE technology. Measurement reference signal(s),may also called CSI (channel state information) reference signal(s), maybe transmitted in physical antenna port(s) or virtualized antennaport(s). Measurement reference signal(s) may be Cell-specific RS usedfor measurement purposes. Channel estimation accuracy may be relativelylower than demodulation RS. CSI reference signal(s) may be defined forLTE-advanced technology and may not be applicable to LTE technology.

In at least one of the various embodiments, uplink physical channel(s)may correspond to a set of resource elements carrying informationoriginating from higher layers. The following example uplink physicalchannel(s) may be defined for uplink: a) Physical Uplink Shared Channel(PUSCH), b) Physical Uplink Control Channel (PUCCH), c) Physical RandomAccess Channel (PRACH), and/or the like. Uplink physical signal(s) maybe used by the physical layer and may not carry information originatingfrom higher layers. For example, reference signal(s) may be consideredas uplink physical signal(s). Transmitted signal(s) in slot(s) may bedescribed by one or several resource grids including, for example,subcarriers and SC-FDMA or OFDMA symbols. Antenna port(s) may be definedsuch that the channel over which symbol(s) on antenna port(s) may beconveyed and/or inferred from the channel over which other symbol(s) onthe same antenna port(s) is/are conveyed. There may be one resource gridper antenna port. The antenna port(s) used for transmission of physicalchannel(s) or signal(s) may depend on the number of antenna port(s)configured for the physical channel(s) or signal(s).

Element(s) in a resource grid may be called a resource element. Aphysical resource block may be defined as N consecutive SC-FDMA symbolsin the time domain and/or M consecutive subcarriers in the frequencydomain, wherein M and N may be pre-defined integer values. Physicalresource block(s) in uplink(s) may comprise of M×N resource elements.For example, a physical resource block may correspond to one slot in thetime domain and 180 kHz in the frequency domain. Baseband signal(s)representing the physical uplink shared channel may be defined in termsof: a) scrambling, b) modulation of scrambled bits to generatecomplex-valued symbols, c) mapping of complex-valued modulation symbolsonto one or several transmission layers, d) transform precoding togenerate complex-valued symbols, e) precoding of complex-valued symbols,f) mapping of precoded complex-valued symbols to resource elements, g)generation of complex-valued time-domain SC-FDMA signal(s) for antennaport(s), and/or the like.

For codeword(s), block(s) of bits may be scrambled with UE-specificscrambling sequence(s) prior to modulation, resulting in block(s) ofscrambled bits. Complex-valued modulation symbols for codeword(s) to betransmitted may be mapped onto one, two, or more layers. For spatialmultiplexing, layer mapping(s) may be performed according to pre-definedformula (s). The number of layers may be less than or equal to thenumber of antenna port(s) used for transmission of physical uplinkshared channel(s). The example of a single codeword mapped to multiplelayers may be applicable when the number of antenna port(s) used forPUSCH is, for example, four. For layer(s), the block of complex-valuedsymbols may be divided into multiple sets, each corresponding to oneSC-FDMA symbol. Transform precoding may be applied. For antenna port(s)used for transmission of the PUSCH in a subframe, block(s) ofcomplex-valued symbols may be multiplied with an amplitude scalingfactor in order to conform to a required transmit power, and mapped insequence to physical resource block(s) on antenna port(s) and assignedfor transmission of PUSCH.

According to some of the various embodiments, data may arrive to thecoding unit in the form of two transport blocks every transmission timeinterval (TTI) per UL cell. The following coding actions may beidentified for transport block(s) of an uplink carrier: a) Add CRC tothe transport block, b) Code block segmentation and code block CRCattachment, c) Channel coding of data and control information, d) Ratematching, e) Code block concatenation. f) Multiplexing of data andcontrol information, g) Channel interleaver, h) Error detection may beprovided on UL-SCH (uplink shared channel) transport block(s) through aCyclic Redundancy Check (CRC), and/or the like. Transport block(s) maybe used to calculate CRC parity bits. Code block(s) may be delivered tochannel coding block(s). Code block(s) may be individually turboencoded. Turbo coded block(s) may be delivered to rate matchingblock(s).

Physical uplink control channel(s) (PUCCH) may carry uplink controlinformation. Simultaneous transmission of PUCCH and PUSCH from the sameUE may be supported if enabled by higher layers. For a type 2 framestructure, the PUCCH may not be transmitted in the UpPTS field. PUCCHmay use one resource block in each of the two slots in a subframe.Resources allocated to UE and PUCCH configuration(s) may be transmittedvia control messages. PUCCH may comprise: a) positive and negativeacknowledgements for data packets transmitted at least one downlinkcarrier, b) channel state information for at least one downlink carrier,c) scheduling request, and/or the like.

According to some of the various aspects of embodiments, cell search maybe the procedure by which a wireless device may acquire time andfrequency synchronization with a cell and may detect the physical layerCell ID of that cell (transmitter). An example embodiment forsynchronization signal and cell search is presented below. A cell searchmay support a scalable overall transmission bandwidth corresponding to 6resource blocks and upwards. Primary and secondary synchronizationsignals may be transmitted in the downlink and may facilitate cellsearch. For example, 504 unique physical-layer cell identities may bedefined using synchronization signals. The physical-layer cellidentities may be grouped into 168 unique physical-layer cell-identitygroups, group(s) containing three unique identities. The grouping may besuch that physical-layer cell identit(ies) is part of a physical-layercell-identity group. A physical-layer cell identity may be defined by anumber in the range of 0 to 167, representing the physical-layercell-identity group, and a number in the range of 0 to 2, representingthe physical-layer identity within the physical-layer cell-identitygroup. The synchronization signal may include a primary synchronizationsignal and a secondary synchronization signal.

According to some of the various aspects of embodiments, the sequenceused for a primary synchronization signal may be generated from afrequency-domain Zadoff-Chu sequence according to a pre-defined formula.A Zadoff-Chu root sequence index may also be predefined in aspecification. The mapping of the sequence to resource elements maydepend on a frame structure. The wireless device may not assume that theprimary synchronization signal is transmitted on the same antenna portas any of the downlink reference signals. The wireless device may notassume that any transmission instance of the primary synchronizationsignal is transmitted on the same antenna port, or ports, used for anyother transmission instance of the primary synchronization signal. Thesequence may be mapped to the resource elements according to apredefined formula.

For FDD frame structure, a primary synchronization signal may be mappedto the last OFDM symbol in slots 0 and 10. For TDD frame structure, theprimary synchronization signal may be mapped to the third OFDM symbol insubframes 1 and 6. Some of the resource elements allocated to primary orsecondary synchronization signals may be reserved and not used fortransmission of the primary synchronization signal.

According to some of the various aspects of embodiments, the sequenceused for a secondary synchronization signal may be an interleavedconcatenation of two length-31 binary sequences. The concatenatedsequence may be scrambled with a scrambling sequence given by a primarysynchronization signal. The combination of two length-31 sequencesdefining the secondary synchronization signal may differ betweensubframe 0 and subframe 5 according to predefined formula (s). Themapping of the sequence to resource elements may depend on the framestructure. In a subframe for FDD frame structure and in a half-frame forTDD frame structure, the same antenna port as for the primarysynchronization signal may be used for the secondary synchronizationsignal. The sequence may be mapped to resource elements according to apredefined formula.

Example embodiments for the physical channels configuration will now bepresented. Other examples may also be possible. A physical broadcastchannel may be scrambled with a cell-specific sequence prior tomodulation, resulting in a block of scrambled bits. PBCH may bemodulated using QPSK, and/or the like. The block of complex-valuedsymbols for antenna port(s) may be transmitted during consecutive radioframes, for example, four consecutive radio frames. In some embodimentsthe PBCH data may arrive to the coding unit in the form of a onetransport block every transmission time interval (TTI) of 40 ms. Thefollowing coding actions may be identified. Add CRC to the transportblock, channel coding, and rate matching. Error detection may beprovided on PBCH transport blocks through a Cyclic Redundancy Check(CRC). The transport block may be used to calculate the CRC parity bits.The parity bits may be computed and attached to the BCH (broadcastchannel) transport block. After the attachment, the CRC bits may bescrambled according to the transmitter transmit antenna configuration.Information bits may be delivered to the channel coding block and theymay be tail biting convolutionally encoded. A tail bitingconvolutionally coded block may be delivered to the rate matching block.The coded block may be rate matched before transmission.

A master information block may be transmitted in PBCH and may includesystem information transmitted on broadcast channel(s). The masterinformation block may include downlink bandwidth, system framenumber(s), and PHICH (physical hybrid-ARQ indicator channel)configuration. Downlink bandwidth may be the transmission bandwidthconfiguration, in terms of resource blocks in a downlink, for example 6may correspond to 6 resource blocks, 15 may correspond to 15 resourceblocks and so on. System frame number(s) may define the N (for exampleN=8) most significant bits of the system frame number. The M (forexample M=2) least significant bits of the SFN may be acquiredimplicitly in the PBCH decoding. For example, timing of a 40 ms PBCH TTImay indicate 2 least significant bits (within 40 ms PBCH TTI, the firstradio frame: 00, the second radio frame: 01, the third radio frame: 10,the last radio frame: 11). One value may apply for other carriers in thesame sector of a base station (the associated functionality is common(e.g. not performed independently for each cell). PHICH configuration(s)may include PHICH duration, which may be normal (e.g. one symbolduration) or extended (e.g. 3 symbol duration).

Physical control format indicator channel(s) (PCFICH) may carryinformation about the number of OFDM symbols used for transmission ofPDCCHs (physical downlink control channel) in a subframe. The set ofOFDM symbols possible to use for PDCCH in a subframe may depend on manyparameters including, for example, downlink carrier bandwidth, in termsof downlink resource blocks. PCFICH transmitted in one subframe may bescrambled with cell-specific sequence(s) prior to modulation, resultingin a block of scrambled bits. A scrambling sequence generator(s) may beinitialized at the start of subframe(s). Block (s) of scrambled bits maybe modulated using QPSK. Block(s) of modulation symbols may be mapped toat least one layer and precoded resulting in a block of vectorsrepresenting the signal for at least one antenna port. Instances ofPCFICH control channel(s) may indicate one of several (e.g. 3) possiblevalues after being decoded. The range of possible values of instance(s)of the first control channel may depend on the first carrier bandwidth.

According to some of the various embodiments, physical downlink controlchannel(s) may carry scheduling assignments and other controlinformation. The number of resource-elements not assigned to PCFICH orPHICH may be assigned to PDCCH. PDCCH may support multiple formats.Multiple PDCCH packets may be transmitted in a subframe. PDCCH may becoded by tail biting convolutionally encoder before transmission. PDCCHbits may be scrambled with a cell-specific sequence prior to modulation,resulting in block(s) of scrambled bits. Scrambling sequencegenerator(s) may be initialized at the start of subframe(s). Block(s) ofscrambled bits may be modulated using QPSK. Block(s) of modulationsymbols may be mapped to at least one layer and precoded resulting in ablock of vectors representing the signal for at least one antenna port.PDCCH may be transmitted on the same set of antenna ports as the PBCH,wherein PBCH is a physical broadcast channel broadcasting at least onebasic system information field.

According to some of the various embodiments, scheduling controlpacket(s) may be transmitted for packet(s) or group(s) of packetstransmitted in downlink shared channel(s). Scheduling control packet(s)may include information about subcarriers used for packettransmission(s). PDCCH may also provide power control commands foruplink channels. OFDM subcarriers that are allocated for transmission ofPDCCH may occupy the bandwidth of downlink carrier(s). PDCCH channel(s)may carry a plurality of downlink control packets in subframe(s). PDCCHmay be transmitted on downlink carrier(s) starting from the first OFDMsymbol of subframe(s), and may occupy up to multiple symbol duration(s)(e.g. 3 or 4).

According to some of the various embodiments, PHICH may carry thehybrid-ARQ (automatic repeat request) ACK/NACK. Multiple PHICHs mappedto the same set of resource elements may constitute a PHICH group, wherePHICHs within the same PHICH group may be separated through differentorthogonal sequences. PHICH resource(s) may be identified by the indexpair (group, sequence), where group(s) may be the PHICH group number(s)and sequence(s) may be the orthogonal sequence index within thegroup(s). For frame structure type 1, the number of PHICH groups maydepend on parameters from higher layers (RRC). For frame structure type2, the number of PHICH groups may vary between downlink subframesaccording to a pre-defined arrangement. Block(s) of bits transmitted onone PHICH in one subframe may be modulated using BPSK or QPSK, resultingin a block(s) of complex-valued modulation symbols. Block(s) ofmodulation symbols may be symbol-wise multiplied with an orthogonalsequence and scrambled, resulting in a sequence of modulation symbols

Other arrangements for PCFICH, PHICH, PDCCH, and/or PDSCH may besupported. The configurations presented here are for example purposes.In another example, resources PCFICH, PHICH, and/or PDCCH radioresources may be transmitted in radio resources including a subset ofsubcarriers and pre-defined time duration in each or some of thesubframes. In an example, PUSCH resource(s) may start from the firstsymbol. In another example embodiment, radio resource configuration(s)for PUSCH, PUCCH, and/or PRACH (physical random access channel) may usea different configuration. For example, channels may be timemultiplexed, or time/frequency multiplexed when mapped to uplink radioresources.

According to some of the various aspects of embodiments, controlmessage(s) or control packet(s) may be scheduled for transmission in aphysical downlink shared channel (PDSCH) and/or physical uplink sharedchannel PUSCH. PDSCH and PUSCH may carry control and datamessage(s)/packet(s). Control message(s) and/or packet(s) may beprocessed before transmission. For example, the control message(s)and/or packet(s) may be fragmented or multiplexed before transmission. Acontrol message in an upper layer may be processed as a data packet inthe MAC or physical layer. For example, system information block(s) aswell as data traffic may be scheduled for transmission in PDSCH. Datapacket(s) may be encrypted packets.

According to some of the various aspects of embodiments, data packet(s)may be encrypted before transmission to secure packet(s) from unwantedreceiver(s). Desired recipient(s) may be able to decrypt the packet(s).A first plurality of data packet(s) and/or a second plurality of datapacket(s) may be encrypted using an encryption key and at least oneparameter that may change substantially rapidly over time. Theencryption mechanism may provide a transmission that may not be easilyeavesdropped by unwanted receivers. The encryption mechanism may includeadditional parameter(s) in an encryption module that changessubstantially rapidly in time to enhance the security mechanism. Examplevarying parameter(s) may comprise various types of system counter(s),such as system frame number. Substantially rapidly may for example implychanging on a per subframe, frame, or group of subframes basis.Encryption may be provided by a PDCP layer between the transmitter andreceiver, and/or may be provided by the application layer. Additionaloverhead added to packet(s) by lower layers such as RLC, MAC, and/orPhysical layer may not be encrypted before transmission. In thereceiver, the plurality of encrypted data packet(s) may be decryptedusing a first decryption key and at least one first parameter. Theplurality of data packet(s) may be decrypted using an additionalparameter that changes substantially rapidly over time.

According to some of the various aspects of embodiments, a wirelessdevice may be preconfigured with one or more carriers. When the wirelessdevice is configured with more than one carrier, the base station and/orwireless device may activate and/or deactivate the configured carriers.One of the carriers (the primary carrier) may always be activated. Othercarriers may be deactivated by default and/or may be activated by a basestation when needed. A base station may activate and deactivate carriersby sending an activation/deactivation MAC control element. Furthermore,the UE may maintain a carrier deactivation timer per configured carrierand deactivate the associated carrier upon its expiry. The same initialtimer value may apply to instance(s) of the carrier deactivation timer.The initial value of the timer may be configured by a network. Theconfigured carriers (unless the primary carrier) may be initiallydeactivated upon addition and after a handover.

According to some of the various aspects of embodiments, if a wirelessdevice receives an activation/deactivation MAC control elementactivating the carrier, the wireless device may activate the carrier,and/or may apply normal carrier operation including: sounding referencesignal transmissions on the carrier, CQI (channel qualityindicator)/PMI(precoding matrix indicator)/RI(ranking indicator)reporting for the carrier, PDCCH monitoring on the carrier, PDCCHmonitoring for the carrier, start or restart the carrier deactivationtimer associated with the carrier, and/or the like. If the devicereceives an activation/deactivation MAC control element deactivating thecarrier, and/or if the carrier deactivation timer associated with theactivated carrier expires, the base station or device may deactivate thecarrier, and may stop the carrier deactivation timer associated with thecarrier, and/or may flush HARQ buffers associated with the carrier.

If PDCCH on a carrier scheduling the activated carrier indicates anuplink grant or a downlink assignment for the activated carrier, thedevice may restart the carrier deactivation timer associated with thecarrier. When a carrier is deactivated, the wireless device may nottransmit SRS (sounding reference signal) for the carrier, may not reportCQI/PMI/RI for the carrier, may not transmit on UL-SCH for the carrier,may not monitor the PDCCH on the carrier, and/or may not monitor thePDCCH for the carrier.

A process to assign subcarriers to data packets may be executed by a MAClayer scheduler. The decision on assigning subcarriers to a packet maybe made based on data packet size, resources required for transmissionof data packets (number of radio resource blocks), modulation and codingassigned to data packet(s), QoS required by the data packets (i.e. QoSparameters assigned to data packet bearer), the service class of asubscriber receiving the data packet, or subscriber device capability, acombination of the above, and/or the like.

According to some of the various aspects of embodiments, packets may bereferred to service data units and/or protocols data units at Layer 1,Layer 2 and/or Layer 3 of the communications network. Layer 2 in an LTEnetwork may include three sub-layers: PDCP sub-layer, RLC sub-layer, andMAC sub-layer. A layer 2 packet may be a PDCP packet, an RLC packet or aMAC layer packet. Layer 3 in an LTE network may be Internet Protocol(IP) layer, and a layer 3 packet may be an IP data packet. Packets maybe transmitted and received via an air interface physical layer. Apacket at the physical layer may be called a transport block. Many ofthe various embodiments may be implemented at one or many differentcommunication network layers. For example, some of the actions may beexecuted by the PDCP layer and some others by the MAC layer.

According to some of the various aspects of embodiments, subcarriersand/or resource blocks may comprise a plurality of physical subcarriersand/or resource blocks. In another example embodiment, subcarriers maybe a plurality of virtual and/or logical subcarriers and/or resourceblocks.

According to some of the various aspects of embodiments, a radio bearermay be a GBR (guaranteed bit rate) bearer and/or a non-GBR bearer. A GBRand/or guaranteed bit rate bearer may be employed for transfer ofreal-time packets, and/or a non-GBR bearer may be used for transfer ofnon-real-time packets. The non-GBR bearer may be assigned a plurality ofattributes including: a scheduling priority, an allocation and retentionpriority, a portable device aggregate maximum bit rate, and/or the like.These parameters may be used by the scheduler in scheduling non-GBRpackets. GBR bearers may be assigned attributes such as delay, jitter,packet loss parameters, and/or the like.

According to some of the various aspects of embodiments, subcarriers mayinclude data subcarrier symbols and pilot subcarrier symbols. Pilotsymbols may not carry user data, and may be included in the transmissionto help the receiver to perform synchronization, channel estimationand/or signal quality detection. Base stations and wireless devices(wireless receiver) may use different methods to generate and transmitpilot symbols along with information symbols.

According to some of the various aspects of embodiments, the transmitterin the disclosed embodiments of the present invention may be a wirelessdevice (also called user equipment), a base station (also calledeNodeB), a relay node transmitter, and/or the like. The receiver in thedisclosed embodiments of the present invention may be a wireless device(also called user equipment-UE), a base station (also called eNodeB), arelay node receiver, and/or the like. According to some of the variousaspects of embodiments of the present invention, layer 1 (physicallayer) may be based on OFDMA or SC-FDMA. Time may be divided intoframe(s) with fixed duration. Frame(s) may be divided into substantiallyequally sized subframes, and subframe(s) may be divided intosubstantially equally sized slot(s). A plurality of OFDM or SC-FDMAsymbol(s) may be transmitted in slot(s). OFDMA or SC-FDMA symbol(s) maybe grouped into resource block(s). A scheduler may assign resource(s) inresource block unit(s), and/or a group of resource block unit(s).Physical resource block(s) may be resources in the physical layer, andlogical resource block(s) may be resource block(s) used by the MAClayer. Similar to virtual and physical subcarriers, resource block(s)may be mapped from logical to physical resource block(s). Logicalresource block(s) may be contiguous, but corresponding physical resourceblock(s) may be non-contiguous. Some of the various embodiments of thepresent invention may be implemented at the physical or logical resourceblock level(s).

According to some of the various aspects of embodiments, layer 2transmission may include PDCP (packet data convergence protocol), RLC(radio link control), MAC (media access control) sub-layers, and/or thelike. MAC may be responsible for the multiplexing and mapping of logicalchannels to transport channels and vice versa. A MAC layer may performchannel mapping, scheduling, random access channel procedures, uplinktiming maintenance, and/or the like.

According to some of the various aspects of embodiments, the MAC layermay map logical channel(s) carrying RLC PDUs (packet data unit) totransport channel(s). For transmission, multiple SDUs (service dataunit) from logical channel(s) may be mapped to the Transport Block (TB)to be sent over transport channel(s). For reception, TBs from transportchannel(s) may be demultiplexed and assigned to corresponding logicalchannel(s). The MAC layer may perform scheduling related function(s) inboth the uplink and downlink and thus may be responsible for transportformat selection associated with transport channel(s). This may includeHARQ functionality. Since scheduling may be done at the base station,the MAC layer may be responsible for reporting scheduling relatedinformation such as UE (user equipment or wireless device) bufferoccupancy and power headroom. It may also handle prioritization fromboth an inter-UE and intra-UE logical channel perspective. MAC may alsobe responsible for random access procedure(s) for the uplink that may beperformed following either a contention and non-contention basedprocess. UE may need to maintain timing synchronization with cell(s).The MAC layer may perform procedure(s) for periodic synchronization.

According to some of the various aspects of embodiments, the MAC layermay be responsible for the mapping of multiple logical channel(s) totransport channel(s) during transmission(s), and demultiplexing andmapping of transport channel data to logical channel(s) duringreception. A MAC PDU may include of a header that describes the formatof the PDU itself, which may include control element(s), SDUs, Padding,and/or the like. The header may be composed of multiple sub-headers, onefor constituent part(s) of the MAC PDU. The MAC may also operate in atransparent mode, where no header may be pre-pended to the PDU.Activation command(s) may be inserted into packet(s) using a MAC controlelement.

According to some of the various aspects of embodiments, the MAC layerin some wireless device(s) may report buffer size(s) of either a singleLogical Channel Group (LCG) or a group of LCGs to a base station. An LCGmay be a group of logical channels identified by an LCG ID. The mappingof logical channel(s) to LCG may be set up during radio configuration.Buffer status report(s) may be used by a MAC scheduler to assign radioresources for packet transmission from wireless device(s). HARQ and ARQprocesses may be used for packet retransmission to enhance thereliability of radio transmission and reduce the overall probability ofpacket loss.

According to some of the various aspects of embodiments, an RLCsub-layer may control the applicability and functionality of errorcorrection, concatenation, segmentation, re-segmentation, duplicatedetection, in-sequence delivery, and/or the like. Other functions of RLCmay include protocol error detection and recovery, and/or SDU discard.The RLC sub-layer may receive data from upper layer radio bearer(s)(signaling and data) called service data unit(s) (SDU). The transmissionentities in the RLC layer may convert RLC SDUs to RLC PDU afterperforming functions such as segmentation, concatenation, adding RLCheader(s), and/or the like. In the other direction, receiving entitiesmay receive RLC PDUs from the MAC layer. After performing reordering,the PDUs may be assembled back into RLC SDUs and delivered to the upperlayer. RLC interaction with a MAC layer may include: a) data transferfor uplink and downlink through logical channel(s); b) MAC notifies RLCwhen a transmission opportunity becomes available, including the size oftotal number of RLC PDUs that may be transmitted in the currenttransmission opportunity, and/or c) the MAC entity at the transmittermay inform RLC at the transmitter of HARQ transmission failure.

According to some of the various aspects of embodiments, PDCP (packetdata convergence protocol) may comprise a layer 2 sub-layer on top ofRLC sub-layer. The PDCP may be responsible for a multitude of functions.First, the PDCP layer may transfer user plane and control plane data toand from upper layer(s). PDCP layer may receive SDUs from upper layer(s)and may send PDUs to the lower layer(s). In other direction, PDCP layermay receive PDUs from the lower layer(s) and may send SDUs to upperlayer(s). Second, the PDCP may be responsible for security functions. Itmay apply ciphering (encryption) for user and control plane bearers, ifconfigured. It may also perform integrity protection for control planebearer(s), if configured. Third, the PDCP may perform header compressionservice(s) to improve the efficiency of over the air transmission. Theheader compression may be based on robust header compression (ROHC).ROHC may be performed on VoIP packets. Fourth, the PDCP may beresponsible for in-order delivery of packet(s) and duplicate detectionservice(s) to upper layer(s) after handover(s). After handover, thesource base station may transfer unacknowledged packet(s)s to targetbase station when operating in RLC acknowledged mode (AM). The targetbase station may forward packet(s)s received from the source basestation to the UE (user equipment).

In this specification, “a” and “an” and similar phrases are to beinterpreted as “at least one” and “one or more.” In this specification,the term “may” is to be interpreted as “may, for example,” In otherwords, the term “may” is indicative that the phrase following the term“may” is an example of one of a multitude of suitable possibilities thatmay, or may not, be employed to one or more of the various embodiments.If A and B are sets and every element of A is also an element of B, A iscalled a subset of B. In this specification, only non-empty sets andsubsets are considered. For example, possible subsets of B={cell1,cell2} are: {cell1}, {cell2}, and {cell1, cell2}.

Many of the elements described in the disclosed embodiments may beimplemented as modules. A module is defined here as an isolatableelement that performs a defined function and has a defined interface toother elements. The modules described in this disclosure may beimplemented in hardware, software in combination with hardware,firmware, wetware (i.e. hardware with a biological element) or acombination thereof, all of which are behaviorally equivalent. Forexample, modules may be implemented as a software routine written in acomputer language configured to be executed by a hardware machine (suchas C, C++, Fortran, Java, Basic, Matlab or the like) or amodeling/simulation program such as Simulink, Stateflow, GNU Octave, orLab VIEWMathScript. Additionally, it may be possible to implementmodules using physical hardware that incorporates discrete orprogrammable analog, digital and/or quantum hardware. Examples ofprogrammable hardware comprise: computers, microcontrollers,microprocessors, application-specific integrated circuits (ASICs); fieldprogrammable gate arrays (FPGAs); and complex programmable logic devices(CPLDs). Computers, microcontrollers and microprocessors are programmedusing languages such as assembly, C, C++ or the like. FPGAs, ASICs andCPLDs are often programmed using hardware description languages (HDL)such as VHSIC hardware description language (VHDL) or Verilog thatconfigure connections between internal hardware modules with lesserfunctionality on a programmable device. Finally, it needs to beemphasized that the above mentioned technologies are often used incombination to achieve the result of a functional module.

The disclosure of this patent document incorporates material which issubject to copyright protection. The copyright owner has no objection tothe facsimile reproduction by anyone of the patent document or thepatent disclosure, as it appears in the Patent and Trademark Officepatent file or records, for the limited purposes required by law, butotherwise reserves all copyright rights whatsoever.

While various embodiments have been described above, it should beunderstood that they have been presented by way of example, and notlimitation. It will be apparent to persons skilled in the relevantart(s) that various changes in form and detail can be made thereinwithout departing from the spirit and scope. In fact, after reading theabove description, it will be apparent to one skilled in the relevantart(s) how to implement alternative embodiments. Thus, the presentembodiments should not be limited by any of the above describedexemplary embodiments. In particular, it should be noted that, forexample purposes, the above explanation has focused on the example(s)using FDD communication systems. However, one skilled in the art willrecognize that embodiments of the invention may also be implemented inTDD communication systems. The disclosed methods and systems may beimplemented in wireless or wireline systems. The features of variousembodiments presented in this invention may be combined. One or manyfeatures (method or system) of one embodiment may be implemented inother embodiments. Only a limited number of example combinations areshown to indicate to one skilled in the art the possibility of featuresthat may be combined in various embodiments to create enhancedtransmission and reception systems and methods.

In addition, it should be understood that any figures which highlightthe functionality and advantages, are presented for example purposesonly. The disclosed architecture is sufficiently flexible andconfigurable, such that it may be utilized in ways other than thatshown. For example, the actions listed in any flowchart may bere-ordered or only optionally used in some embodiments.

Further, the purpose of the Abstract of the Disclosure is to enable theU.S. Patent and Trademark Office and the public generally, andespecially the scientists, engineers and practitioners in the art whoare not familiar with patent or legal terms or phraseology, to determinequickly from a cursory inspection the nature and essence of thetechnical disclosure of the application. The Abstract of the Disclosureis not intended to be limiting as to the scope in any way.

Finally, it is the applicant's intent that only claims that include theexpress language “means for” or “step for” be interpreted under 35U.S.C. 112, paragraph 6. Claims that do not expressly include the phrase“means for” or “step for” are not to be interpreted under 35 U.S.C. 112,paragraph 6.

What is claimed is:
 1. A wireless device comprising: a) one or morecommunication interfaces; b) one or more processors; and c) memorystoring instructions that, when executed, cause the wireless device to:i) generate a first signal, by at least demodulating, descrambling anddecoding signals received on a plurality of OFDM subcarriers in a firstOFDM symbol; ii) produce a processed first signal, by at least encoding,scrambling, modulating and scaling said first signal; iii) generate asecond signal, by subtracting said processed first signal from receivedsignals on said plurality of OFDM subcarriers in said first OFDM symbol;iv) produce a control format indicator, by at least demodulating,descrambling and decoding said second signal; and v) determine number ofOFDM symbols of a control region of a base station employing saidcontrol format indicator.
 2. The wireless device of claim 1, whereinsaid control format indicator comprises two bits of information.
 3. Thewireless device of claim 1, wherein said control format indicator isencoded employing a repetition code.
 4. The wireless device of claim 1,wherein said control format indicator is received over sixteenmodulation symbols.
 5. A wireless device comprising: a) one or morecommunication interfaces; b) one or more processors; and c) memorystoring instructions that, when executed, cause the wireless device to:i) generate a first signal, by at least demodulating, descrambling anddecoding signals received on a plurality of OFDM subcarriers in a firstOFDM symbol; ii) produce a processed first signal, by at least encoding,scrambling, modulating and scaling said first signal; iii) generate asecond signal, by subtracting said processed first signal from receivedsignals on said plurality of OFDM subcarriers in said first OFDM symbol;iv) produce a physical broadcast message, by at least demodulating,descrambling and decoding said second signal; and v) determine aplurality of system parameters of a base station employing said physicalbroadcast message.
 6. The wireless device of claim 5, wherein saidphysical broadcast message is encoded employing: a) a convolutionalcode; and b) a repetition code.
 7. The wireless device of claim 5,wherein said physical broadcast message reception reoccurs periodicallywith a fixed period.
 8. The wireless device of claim 5, wherein saidphysical broadcast message is received over seventy-two OFDM subcarrierssubstantially in the center of a carrier.
 9. The wireless device ofclaim 5, wherein said plurality of system parameters comprise: a) systembandwidth information; b) HARQ indicator channel structure information;and c) eight most significant bits of a system frame number.
 10. Awireless device comprising: a) one or more communication interfaces; b)one or more processors; and c) memory storing instructions that, whenexecuted, cause the wireless device to: i) produce a first plurality ofcorrelation values, by correlating received signals with a firstplurality of predetermined synchronization signals, said receivedsignals received on a plurality of OFDM subcarriers in a subset of OFDMsymbols; ii) identify a first synchronization signal transmitted by afirst base station, employing said first plurality of correlationvalues; iii) process said first synchronization signal, by at leastscaling said first synchronization signal by a scaling factor; iv)generate an updated received signal, by subtracting said processed firstsynchronization signal from received signals on said plurality of OFDMsubcarriers in said subset of OFDM symbols; and v) identify a secondsynchronization signal transmitted by a second base station, employingsaid updated received signal.
 11. The wireless device of claim 10,wherein said second base station is of a different base station typethan said first base station.
 12. The wireless device of claim 10,wherein said first synchronization signal has a highest correlationvalue among said first plurality of correlation values.
 13. The wirelessdevice of claim 10, wherein said first synchronization signal istransmitted over seventy-two OFDM subcarriers substantially in thecenter of said carrier.
 14. The wireless device of claim 10, whereinsaid scaling factor is a function of characteristics of a wirelesschannel.
 15. The wireless device of claim 10, wherein said instructionsfurther cause the wireless device to obtain timing information of saidsecond base station, employing said second synchronization signal.